Ziegler_Nichols,Cohen Coon, PID, Coughanowr, unit step

Hi everybody, I need your help. I currently learning about ziegler nichols and cohen coon method to determine Kc, ti, td in PID controller. My reference book is Process Systems Analysis and Control Third Edition by Donald R. Coughanowr and Steven E. LeBlanc. I try to re-create the block diagram in simulink. But when I input the value of Kc, ti, and td after calculate them using these method, the graphs didn't resemble like the one in my reference book (in figure 18-10 it supposed to decays, but my graphs are unstable and keep getting larger). I suspect I haven't set the parameter value of the unit step correctly. I don't understand what's the effect of each parameter cause my reference book didn't explain. If anyone familiar with the book or the effect of each unit step parameter, I would appreciate the help. Or if I had the block diagram all wrong, I hoping for corrections. Thank You.

Answer 1

[Sadagopan]

In the PID Block You should enter Kp, Ki = Kp/Ti and Kd = Kp*Td Value no Ti and Td values directly.